Antisera from guinea pigs immunized against individual human rhinovirus (HRV) serotypes were used to determine reactivity with the capsid surface peptides (VP1, VP2, VP3) of HRV serotype 2 (HRV2) in an immunoblot system. HRV2 was purified by CsC1 gradient, separated on polyacrylamide, and transferred to nitrocellulose membranes. Serum IgG binding was detected by immunoperoxidase technique. Only the serum specific for HRV2 neutralized HRV2. However, approx-imately two-thirds of the 53 tested sera (which were representative of HRV in both of the receptor and both of the antiviral agent binding groups) contained IgG against VP1 and in some instances VP2 or, more rarely, VP3 of HRV2. The greatest reactivity was identified for HRV in the same receptor and antiviral group as HRV2; least reactivity was for HRV in neither the same receptor or antiviral group. However, antiserum against HRV 31 (in the same receptor and antiviral group as HRV2) consistently failed to react with the peptides of HRV2. Antiserum for HRV89 (same antiviral but different receptor group) reacted strongly which is notable since HRV2 and HRV89 are relatively closely related by peptide sequences. Antiserum to HRV87 (which does not clearly belong to either specifically identified receptor group) reacted with VP1 of HRV2. In preliminary studies using the purified capsid peptides of HRV14 for immunoblot antigens, the pattern of reactivity suggests mutually exclusive reactivity compared to the data obtained with HRV 2. The data suggest that immunoblot identifies conserved HRV epitopes and may be an additonal tool for determining rhinovirus evolution.